The human body can reduce the overall efficiency of a radio. Two of the mechanisms for this loss can be mismatch loss and absorptive loss. As the phone's environment changes and the user holds the phone in various ways, the antenna of the radio is “de-tuned”, which can cause an impedance mismatch between the antenna and the rest of the radio. This results in power being reflected and wasted as heat. An even greater amount of power can also be lost due to absorption of energy into the human body.
Electrically steerable antennas for communication devices are known. Either the main lobe of the antenna or the null(s) of the antenna can be steered by means of altering the RF currents on the antenna or ground plane below the antenna, or changing the phase of the signal applied to the antenna(s). Furthermore, analog or digital components can be placed on the antenna itself to change the electrical characteristics and thus “steer” the antenna. Often, when the ground plane of the antenna is as small as the main circuit board found in typical mobile phones, the amount of steering achievable by such methods is limited. However, the amount of antenna pattern steering may be sufficient to steer a significant amount of the pattern away from near field objects, such as the user.